Special Issue "Synthesis and Properties of Bulk Nanostructured Metallic Materials"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 31 December 2017

Special Issue Editor

Guest Editor
Prof. Dr. Byungmin Ahn

Department of Materials Science and Engineering & Energy Systems Research, Ajou University, Suwon 443-749, South Korea
Website | E-Mail

Special Issue Information

Dear Colleagues,

Bulk nanostructured materials (BNMs) are defined as polycrystalline bulk solids with nanocrystalline (NC) or ultrafine-grained (UFG) microstructures. These BNMs have received increasing attention because of the potential of their improved properties and promising applications compared to conventional coarse-grained materials with the same chemical compositions. For example, BNMs exhibit superior mechanical properties, such as strength or hardness, unachievable with conventional counterparts. This is generally attributed to a large portion of the volume being associated with disordered grain boundary regions because of the extremely fine grain sizes of BNMs. Recent advances in the synthesis and processing techniques of BNMs drive our need to understand the underlying fundamental phenomena as well as their significant properties. Research on the synthesis and properties of BNMs is one of the most emerging fields in advanced structural materials systems. This Special Issue covers a wide scope in the research field of BNMs, and we cordially invite original research articles and reviews of the recent achievements on the following subjects of BNMs:

  • Synthesis and processing techniques
  • Development of novel experimental methods
  • Advances in severe plastic deformation (SPD) processing and SPD materials
  • Powder processing and powder metallurgy materials
  • Deformation mechanisms and experimental mechanics
  • Mechanical and physical properties
  • Microstructural evolution and characterization
  • Computational and analytical modeling
  • Structural, functional, and biomedical applications

Prof. Dr. Byungmin Ahn
Guest Editor

Manuscript Submission Information

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Keywords

  • Bulk nanostructured materials
  • Nanocrystalline materials
  • Ultrafine-grained materials
  • Severe plastic deformation
  • Grain refinement
  • Mechanical properties
  • Microstructure

Published Papers (5 papers)

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Research

Open AccessArticle Peculiar Spatiotemporal Behavior of Unstable Plastic Flow in an AlMgMnScZr Alloy with Coarse and Ultrafine Grains
Metals 2017, 7(9), 325; doi:10.3390/met7090325
Received: 20 July 2017 / Revised: 14 August 2017 / Accepted: 18 August 2017 / Published: 23 August 2017
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Abstract
The work addresses the effects of nanosize particles and grain refinement on the patterns of stress serrations and kinematics of deformation bands associated with the Portevin–Le Chatelier instability of plastic flow. Ultra-fine-grained microstructure was obtained using equal-channel angular pressing of the initial coarse-grained
[...] Read more.
The work addresses the effects of nanosize particles and grain refinement on the patterns of stress serrations and kinematics of deformation bands associated with the Portevin–Le Chatelier instability of plastic flow. Ultra-fine-grained microstructure was obtained using equal-channel angular pressing of the initial coarse-grained alloy. Tensile tests were carried out on flat specimens at strain rates in the range from 3 × 10−5 to 1.4 × 10−2 s−1. Using local extensometry techniques, it was found that the presence of nanoscale precipitates promotes quasi-continuous propagation of deformation bands in the entire strain-rate range. The grain refinement leads to a transition to relay-race propagation at high strain rates and static strain localization at low rates. The results are discussed from the viewpoint of competition between various dynamical modes of plastic deformation associated with collective dynamics of dislocations. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle High-Yield One-Pot Recovery and Characterization of Nanostructured Cobalt Oxalate from Spent Lithium-Ion Batteries and Successive Re-Synthesis of LiCoO2
Metals 2017, 7(8), 303; doi:10.3390/met7080303
Received: 11 July 2017 / Revised: 27 July 2017 / Accepted: 2 August 2017 / Published: 7 August 2017
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Abstract
A complete recycling process for the cathode material of spent lithium-ion batteries is demonstrated with a simple two-step process comprised of one-pot cobalt recovery to nanostructured materials and single step synthesis of LiCoO2. For the facile and efficient recovery of cobalt,
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A complete recycling process for the cathode material of spent lithium-ion batteries is demonstrated with a simple two-step process comprised of one-pot cobalt recovery to nanostructured materials and single step synthesis of LiCoO2. For the facile and efficient recovery of cobalt, we employ malic acid as a leaching agent and oxalic acid as a precipitating agent, resulting in nanostructured cobalt oxalate. X-ray diffraction and Fourier transform infrared spectroscopy (FT-IR) analysis clearly show that cobalt species are simultaneously leached and precipitated as cobalt oxalate with a high yield of 99.28%, and this material can then be used as a reactant for the synthesis of LiCoO2 for use as a cathode material. In addition to its advantages in simplifying the process, the proposed method allows for not only enhancing the efficiency of cobalt recovery, but also enabling reaction without a reducing agent, H2O2. Through successive single-step reaction of the obtained cobalt oxalate without any purification process, LiCoO2 is also successfully synthesized. The effect of the annealing temperature during synthesis on the nanostructure and charge–discharge properties is also investigated. Half-cell tests with recycled LiCoO2 exhibit a high discharge capacity (131 mA·h·g−1) and 93% charge–discharge efficiency. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Effects of SiC Nanoparticles on the Properties of Titanium-Matrix Foams Processed by Powder Metallurgy
Metals 2017, 7(8), 296; doi:10.3390/met7080296
Received: 9 June 2017 / Revised: 17 July 2017 / Accepted: 24 July 2017 / Published: 3 August 2017
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Abstract
Metal-matrix foams are used widely for structural applications such as impact energy absorption, vibration resistance and weight reduction. In this study titanium nanocomposite foams with different porosity percentages were produced using TiH2, as foaming agent, by powder metallurgy technique. At first,
[...] Read more.
Metal-matrix foams are used widely for structural applications such as impact energy absorption, vibration resistance and weight reduction. In this study titanium nanocomposite foams with different porosity percentages were produced using TiH2, as foaming agent, by powder metallurgy technique. At first, raw materials including titanium powder and different weight percentages of SiC nanoparticles were mixed and then different amounts of TiH2 were added to the mixture. The mixture was compacted at 200 MPa. The samples were heat treated in two stages, first at 400 °C for 1 h, as a partial sintering, and then at 1050 °C for 2 h, as foaming treatment. Mechanical and structural properties such as compressive strength, energy absorption, porosity percentage and relative density of samples were measured and compared together. Thermo gravimetric analysis (TGA), differential thermal analysis (DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed on foaming agent and samples. The results showed uniform distribution of SiC nanoparticles in titanium matrix and also homogenous pore structure. It was concluded that with increasing SiC weight percent, relative density is increased to 0.43 in the sample with 1.5 wt % SiC. Besides, the measured compressive strength of samples was in the range of 14.4–32.3 MPa. Moreover, it was concluded that the energy absorption of samples increases with increasing SiC nano particles up to 33.09 MJ/m3. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Enhanced Surface Precipitates on Ultrafine-Grained Titanium in Physiological Solution
Metals 2017, 7(7), 245; doi:10.3390/met7070245
Received: 17 May 2017 / Revised: 15 June 2017 / Accepted: 27 June 2017 / Published: 1 July 2017
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Abstract
Enhanced cell adherence to the surface of nanocrystallized commercially pure titanium (CP–Ti) was observed by several authors. However, the understanding of the surface modification of Ti in a physiological solution due to nanocrystallized grain size has not been reached. In this work, equal
[...] Read more.
Enhanced cell adherence to the surface of nanocrystallized commercially pure titanium (CP–Ti) was observed by several authors. However, the understanding of the surface modification of Ti in a physiological solution due to nanocrystallized grain size has not been reached. In this work, equal channel angular pressing (ECAP) was applied to manufacturing ultrafine grained CP–Ti. Martensite and Widmanstatten microstructures were also obtained for comparison. The CP–Ti pieces with different microstructures were subjected to soaking tests in a simulated body fluid. Electrochemical impedance spectroscopy (EIS) measurements, X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM), energy dispersive spectrometer (EDS) were used to characterize the surfaces. The results show the surface precipitates mainly contain Ti, O, Ca and P. The quantity of precipitates on ECAPed CP–Ti is the largest among different specimens corresponded to the observation of the thickest layer formation on ECAPed CP–Ti found by EIS. EDS results show more CaPO and less Ti are included on ECAPed Ti comparing to the deposits on other two types of specimens. Smaller numbers of precipitates and denser film are produced on the surface of the water-quenched CP–Ti. The regeneration kinetics of the CaP precipitates evaluated by Gibbs free energy is introduced to interpret the precipitating behaviors on different CP–Ti specimens. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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Open AccessArticle Synthesis and Characterization of Nano-Particles of Niobium Pentoxide with Orthorhombic Symmetry
Metals 2017, 7(4), 142; doi:10.3390/met7040142
Received: 27 March 2017 / Revised: 10 April 2017 / Accepted: 13 April 2017 / Published: 19 April 2017
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Abstract
In this work, a set of nanoparticles of Nb2O5 nanoparticles were grown by both the Pechini and the sol-gel methods. The amorphous materials were calcined at 650 #xB0;C or at 750 °C. X-ray diffraction, scanning electron microscopy, luminescence and Raman
[...] Read more.
In this work, a set of nanoparticles of Nb2O5 nanoparticles were grown by both the Pechini and the sol-gel methods. The amorphous materials were calcined at 650 #xB0;C or at 750 °C. X-ray diffraction, scanning electron microscopy, luminescence and Raman spectroscopy were used in order to characterize the materials. From the study, it is possible to state that the method of production of nanoparticles, beyond the temperature of synthesis, has a great influence on whether the phase produced is hexagonal or orthorhombic. Additionally, compared to de Sol-gel method, the Pechini method produced samples with smaller particle sizes. The photoluminescence spectra of niobium pentoxide nanostructure materials show that the emission peaks are positioned between 334 to 809 nm and there is a change of intensity which varies depending on the synthesis route used. High pressure Raman spectra at room temperature were obtained from two samples grown by the sol-gel method. Up to 6 GPa, where it is possible to observe the Raman bands, no modification other than the increase of disorder was observed, and this can be associated with a change of phase. Full article
(This article belongs to the Special Issue Synthesis and Properties of Bulk Nanostructured Metallic Materials)
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